Vessels, Net (Details)	3 Months Ended
	Jun. 30, 2018 USD ($) item	Mar. 31, 2018 USD ($)
Accumulated depreciation
Vessels, net	$ 1,523,143,231	$ 1,539,111,833
Vessels
Cost
Balance at the beginning of the period	1,728,987,980
Other additions	131,193
Balance at the end of the period	1,729,119,173
Accumulated depreciation
Balance at the beginning of the period	(189,876,147)
Impairment	0
Depreciation	(16,099,795)
Balance at the end of the period	$ (205,975,942)
Number of vessels with capital improvements | item	1
Mortgaged VLGC vessels, carrying value	$ 1,523,100,000	$ 1,539,100,000